The present invention relates to an indexable insert, especially an indexable insert having a heat absorbing performance, and a heat absorption indexable tool using the insert.
In the prior art, cutting oil has been generally used in a cutting work of a metal. Recently, however, it is desired from the view point of the environmental problem or the production cost to reduce the cutting oil, as might otherwise be consumed in a large quantity. However, the cutting oil has a high cooling effect, and it is directly connected to a rise in the tool cost and a drop in the working efficiency to stop the use of the cutting oil. Therefore, there has been demanded the development of a cooling method or a cutting method in place of the method using the cutting oil.
As this counter-measure, there has been proposed in the prior art the method of eliminating the cutting heat and lubricating by convecting a small amount of cutting liquid and/or gas to a cutting point, such as the MQL cutting method, the cold-air blast cutting method or the nitrogen blast cutting method using vegetable oil.
However, these methods are proper for the aspect of the environmental problem but still have various problems unsolved. More specifically, the case of the MQL cutting method cannot be said a complete dry cutting method, and has a problem that the cutting conditions for its effect are limited to the cutting mode of the reach of sufficient mist. The cold-air blast cutting method is required to have an expensive apparatus for establishing a cold wind of xe2x88x9240xc2x0 C. and to have a frost resistance at the feed circuit and the blow-off outlet. Thus, the cold-air blast cutting method is still troubled in that it takes excess costs and troubles and in that the wind noise by the cold-wind blast causes the pollution problem.
As another measure, there has been proposed a method for cooling the tool. In WO95/29030, for example, there has been proposed a drill, in which a passage for a cooling medium to pass through is formed in the drill shaft. In Unexamined Published Japanese Patent Application No. 10-58220, it has been proposed to form a passage in an end mill for passing a cooling liquid therethrough.
In all of these methods, a shaft-shaped solid tool is cooled always at a fixed position, so that the methods can be easily applied. In the indexable insert used as most generally as the cutting tool, that is, in the insert to be discarded when the cutting edges (the cutting corners) are discarded when the they come to the end of life, however, the cutting edges are present in plurality at a plurality of discrete portions so that they are sequentially changed as they are used. Therefore, the portions to be cooled are changed to make it difficult to apply the aforementioned methods, and no notable proposal has been made in the prior art.
The present invention has been conceived to solve the above-specified problems and has an object to provide a heat absorption indexable insert which can exhibit an effect of tool wear resistance similar to that of the cutting oil using case in a dry cutting operation, which can absorb a plurality of cutting edges (or corners) at discrete positions efficiently, and which can be easily manufactured with a simple structure, and an indexable tool to which the indexable insert is applied.
In order to achieve the above-specified object, according to the present invention, in an indexable tool to be attached, when used, to a shank or holder having fluid inlet and outlet passages, there is provided a heat absorption indexable insert comprising: a corridor-shaped cooling passage disposed inside of a plurality of corners and circulating the vicinities of the individual corners sequentially; and a connecting passage arranged in an end portion region of said cooling passage so as to communicate with said inlet passage and said outlet passage even when any corner is used.
According to this construction, the heat absorption rate can be raised no matter what corner might be used as any of cutting edges, to absorb and release the cutting heat efficiently from the inside of the insert. Without using the cutting oil, therefore, the environment can be satisfied, and the heat release rate of the cutting heat is increased to provide an effect of tool wear resistance similar to that of the wet method.
According to a first mode, said cooling passage and said connecting passage are individually shaped to have the closed sectional shapes, i.e., or the holes. This mode can be applied to the case in which the indexable insert is of a positive type or of a negative type. In the case of the positive type, the connecting passage is opened only in the lower face of the insert. In the case of the negative type, the connecting passage is extended through the insert in the thickness direction and is opened in the upper and lower faces of the insert.
According to this construction, the cutting heat of the cutting edge can be efficiently absorbed no matter what type the indexable insert might take. Moreover, the cooling passage and the connecting passage are present as cavities in the insert to provide an advantage that it is easy to do the work of crushing the used heat absorption indexable insert for reuse. Where the connecting passage is extended through the insert in the thickness direction, the heat can be absorbed from all the corners of the surface and back of the insert merely by laying the seal member on the heat absorption indexable insert.
In a second mode, said cooling passage and said connecting passage are individually formed into a groove-shaped section having openings in the lower face of the insert. In this case, the indexable insert is of the positive type.
The representative construction for enabling the cooling passage and the connecting passage to communicate with the inlet passage and the outlet passage selectively no matter what corner might be used will be enumerated, as follows.
1) The single connecting passage is disposed at the center of a polygonal indexable insert; connecting passages are disposed on straight lines joining the individual corners to be used as cutting edges and said center and at positions equidistant from the center; and the center connecting passage communicates with one end portion of the cooling passage whereas the remaining connecting passages communicate with the other end portion of the cooling passage.
In this case, the center connecting passage functions as the inlet passage at all times whereas the other connecting passages around the center one function as the outlet passages.
2) The connecting passages are disposed on diagonal lines joining the corners to be used as the cutting edges of a polygonal indexable insert and at positions equidistant from the insert center, and the connecting passages belonging to one side region halved from the center of the sides of the insert communicate with one end portion of the cooling passage whereas the connecting passages belonging to the other side region communicate with the other end portion of the cooling passage. In this case, one of the connecting passages belonging to one of the regions functions as an inlet passage whereas the connecting passages belonging to the other region function as an outlet passage.
Where these passage constructions 1) and 2) are adopted, the inlet passage and the outlet passage on the shank or holder side may be formed to have the spacing and direction identical to those of said connecting passages. Thus, when the corner to be used of the heat absorption indexable insert is changed, the cooling passage is automatically caused by the connecting passages to communicate with the inlet passage and the outlet passage. No matter what corner might be used as the cutting point, therefore, it is possible to provide an indexable tool which can be easily used to absorb the heat from the cutting edges. In the case of the passage construction 2), no connecting passage is formed at the center of the insert. Therefore, it is possible to make the number of connecting passages smaller than that of the case 1), and to open a hole at the insert center for inserting the fixing pin thereby to find a suitable application to the screw-on type.
In the indexable insert thus far described, the cooling passage and the connecting passages may preferably be formed by any of the following methods.
In the first mode, the cooling passage and the connecting passages are prepared by laminating and joining two halved inserts (e.g., the tentatively or completely sintered compacts) having grooves.
In the second mode, the cooling passage and the connecting passages are prepared by causing a core having a shape corresponding thereto to disappear at the time of sintering a compact.
In the third mode, the cooling passage and the connecting passages are prepared by compacting with a mold having a rising mold face corresponding thereto.
The first mode and the second mode are suitable for the case in which the cooling passage and the connecting passages are shaped to have the closed section. The second mode is advantageous in the simple process because the insert has no seam that it has no anxiety in strength or water leakage. The third mode is applied to the case in which the cooling passage and the connecting passages are shaped to have grooved section, and is advantageous in that they can be manufactured at a reasonable price by the simple process.
The present invention includes the heat absorption indexable tool using the aforementioned indexable insert. One heat absorption indexable tool is characterized by comprising a shank or holder having fluid inlet and outlet passages; an indexable type tool including an indexable insert having a plurality of corners and attached to the shank or holder; and cooling means connected to the inlet passage and the outlet passages, and is characterized: in that said indexable insert includes: a corridor-shaped cooling passage disposed inside of a plurality of corners and circulating the vicinities of the individual corners sequentially; and at least two connecting passages arranged in the end region of said cooling passage so as to communicate with said inlet passage and said outlet passage even when any of the corners is used; and in that said cooling means includes a pump for pumping a cooling fluid to the inlet passage.
Moreover, another heat absorption indexable tool of the present invention is characterized in that said cooling means includes a pump for sucking a cooling fluid from the outlet passage. In the case of this method, the indexable insert can be exemplified by that the cooling passage and the connecting passages are shaped to have the groove section, so that the tool can be manufactured at a reasonable cost.
Although the remaining features and advantages of the present invention will be described, it is apparent that the present invention should not be limited to the constructions exemplified in its embodiments so long as they are provided with the fundamental characteristics of the present invention, and that the present invention can be modified and corrected by those skilled in the art in various manners without departing from the scope thereof.